Thomas L. Theis

Environmental assessment of ash disposal

Abstract Combustion processes for power generation or waste volume reduction result in the generation of mostly inorganic ash residues. Recycling or reuse of these materials is sometimes possible; however, presently, the major portion must be disposed of in an environmentally acceptable way. In this review, the physical and chemical properties of these ashes are presented, and their suitability for various purposes are assessed. Included is information on leachate generation and how inorganic species interact and are transported in porous media. In view of these principles, appropriate environmental control strategies are presented and discussed.

A uniform definition and quantitative basis for industrial ecology

Abstract Industrial ecology (IE) has been characterized by a fragmented approach encompassing a number of different perspectives and analytical techniques. A uniform framework has yet to be established or proposed. This paper partially addresses this shortcoming by tracing some of the historical and intellectual antecedents of the field, providing a clear and concise lexicon of the biological analogue, and contrasting the two most promising analytical methods by which IE research may be carried out: life cycle assessment (LCA) and systems analysis. Although a number of comparative environmental metrics may be employed in cost-minimization or thermodynamic efficiency studies, no single measure is sufficiently developed to prioritize among qualitatively disparate types of environmental impacts. It is argued herein that the concept of chemical exergy of mixing may be the most promising basis for the development of a uniform, broad-based measure of chemical pollution, and that such a measure could significantly advance a scientific approach to IE. Some theoretical background is presented, although the reasoning herein is intended to be accessible to an interdisciplinary audience.

Kinetic studies of cadmium and ferricyanide adsorption on goethite

Batch and dynamic column methods were used to investigate the sorption rates of ferricyanide ion and cadmium on goethite under constant-pH conditions. Results indicated the rate of adsorption for ferricyanide to be limited by surface mass transfer. Analysis of column data showed mass transfer to be rate limiting during initial adsorption of cadmium and a secondary reaction to be rate limiting overall with a forward conditional rate constant of 3.02 x 10/sup -3/ L mol/sup -1/ s/sup -1/. Total reactive surface site density for cadmium agreed well with the value obtained from more dilute batch studies. In contrast, the data for ferricyanide showed a single-reaction approach to be sufficient; however, the batch-derived site density was substantially greater than that obtained from the column. These results are discussed in view of the surface-bonding character of these solutes, and implications for laboratory-generated partitioning data are examined.

Leachate characteristics and composition of cyanide-bearing wastes from manufactured gas plants.

Past activities associated with the manufacture of gas from hydrocarbon feedstocks resulted in the generation of substantial quantities of cyanide-bearing wastes produced as a result of product gas cleanup for the removal of hydrogen sulfide and hydrogen cyanide. Large quantities of these sites have been found at several manufactured gas plant sites. It was the purpose of this study to address questions relating to the availability of cyanide to the environment and to determine the chemical forms of cyanide in the waste. This information is necessary in order to assess the toxicity and possible methods of treatment and disposal of the material

A new framework for urban sustainability assessments: Linking complexity,information and policy

Abstract Urban systems emerge as distinct entities from the complex interactions among social, economic and cultural attributes, and information, energy and material stocks and flows that operate on different temporal and spatial scales. Such complexity poses a challenge to identify the causes of urban environmental problems and how to address them without causing greater deterioration. Planning has traditionally focused on regulating the location and intensity of urban activities to avoid environmental degradation, often based on assumptions that are rarely revisited and producing ambiguous effects. The key intellectual challenge for urban policy-makers is a fuller understanding of the complexity of urban systems and their environment. We address this challenge by developing an assessment framework with two main components: (1) a simple agent-based model of a hypothetical urbanizing area that integrates data on spatial economic and policy decisions, energy and fuel use, air pollution emissions and assimilation, to test how residential and policy decisions affect urban form, consumption and pollution; (2) an information index to define the degree of order and sustainability of the hypothetical urban system in the different scenarios, to determine whether specific policy and individual decisions contribute to the sustainability of the entire urban system or to its collapse.

Phosphorus dynamics in hypereutrophic lake sediments

Abstract The sediments of two hypereutrophic lakes (Stone Lake, Michigan and Lake Charles East, Indiana) were studied to determine phosphorus sorption and release tendencies as they vary seasonally. Techniques used were chemical extractions of phosphorus forms from core fractions and the incubation of undisturbed cores in the laboratory under ambient conditions of temperature and dissolved oxygen. The uptake of phosphorus during aerobic periods was found to be in accord with previously observed trends in that the amount sorbed was proportional to overlying phosphorus concentration supporting an adsorption type of model. Phosphorus was given off during anoxic periods, however, the specific release rates could not be correlated with the gradient of interstitial phosphorus to overlying phosphorus concentrations as reported by others. Rather, release rates were closely correlated with average interstitial phosphorus concentrations. A diffusion model is presented, applicable to systems similar to those studied, in which soluble interstitial phosphorus varies from a greatly elevated concentration in close proximity to sediment particle surfaces to levels approaching those of overlying phosphorus.

Comparison of life-cycle inventory databases: A case study using soybean production

Three established life-cycle inventories of agricultural operations were used to generate air emissions data for soybean production: the greenhouse gases, regulated emissions, and energy use in transportation (GREET) model; the economic input-output life-cycle assessment (EIO-LCA) model; and SimaPro software equipped with the Franklin database. EIO-LCA and GREET baseline data were compared to evaluate differences in boundary definitions that apply specifically to U.S. soybean agriculture and processing, which resulted in several major findings. The EIO model estimated for emissions of particulate matter less than 10 micrograms (PM10) resulting from wind erosion that were not included in GREET, but neglected indirect nitrous oxide (N2O) and nitrogen oxides (NOx) emissions from fertilizer application. EIO also assumed significantly lower process energy requirements and lower volatile organic compounds (VOC) for soybean crushing and oil extraction. The GREET and SimaPro models were compared using identical boundary and assumption data, to reveal major discrepancies in fundamental assumptions of energy inventories. Key emission factors varied by several orders of magnitude for basic energy generation and combustion processes, potentially impacting results for any inventory analysis that contains significant energy consumption. The Franklin database assumed VOC and sulfur oxides (SOx) emissions more than an order of magnitude higher than GREET for all categories investigated, with significantly lower N2O and methane (CH4) emission factors.

Colloid Aggregation: Numerical Solution and Measurements

Abstract A model has been developed that describes the kinetics of particle aggregation by a numerical solution of the von Smoluchowski equation. While the complete model incorporates surface chemical phenomena, this paper discusses only the physical aggregation process, and focuses on long-term aggregation where aggregates composed of many primary particles (up to 2000) are formed. Model simulations were compared with laboratory experiments that were conducted with hematite spheres aggregating with no applied shear stress. Comparison was achieved by minimizing the sum of squared differences between the model and experimental data using two fitting parameters: the collision efficiency and the fractal dimension of the aggregates. The model was sensitive to the two parameters, which had a small degree of dependence on one another as evidenced by the orientation of the joint confidence regions. Estimates of the fractal dimension varied inversely with collision efficiency and were between 1.25 and 1.5; lower than many estimates by others for diffusion-controlled processes but consistent with cluster–cluster aggregation of aggregates comprised of very dense particles. The collision efficiency was estimated to be 1×10−4 for slow aggregation conditions, and 2×10−4 under rapid aggregation; these values reflect inclusion of hydrodynamic interactions and their significance in a system dominated by differential settling.

Exergetic pollution potential: Estimating the revocability of chemical pollution

The waste exergy approach to quantitative comparison of environmental impacts is considerably improved by proposing a separate accounting of material and energetic waste exergy and the implications are discussed within the context of sustainability. The exergy of mixing of a waste stream is found to be particularly well suited to an exergetic definition of chemical pollution and a correlative relationship with environmental pollutant cost (EPC) is suggested. A comprehensive measure of chemical environmental impact called pollution potential is defined as temperature multiplied by the change in configurational entropy per mole of pollutant in the environment. The result is related to the ideal thermodynamic work of chemical separation per mole required to instantaneously revoke a chemical pollutant, thereby returning the environment to a pristine reference condition. The current pollution potentials and total exergy of revocation of several notable atmospheric pollutants are estimated. Carbon dioxide is found to have low pollution potential in comparison to most halogenated hydrocarbons, but the vast quantities of anthropogenic carbon dioxide in the atmosphere would require much more total exergy of separation to revoke.

Life Cycle Payback Estimates of Nanosilver Enabled Textiles under Different Silver Loading, Release, And Laundering Scenarios Informed by Literature Review.

Silver was utilized throughout history to prevent the growth of bacteria in food and wounds. Recently, nanoscale silver has been applied to consumer textiles (nAg-textiles) to eliminate the prevalence of odor-causing bacteria. In turn, it is proposed that consumers will launder these items less frequently thus, reducing the life cycle impacts. While previous studies report that laundering processes are associated with the greatest environmental impacts of these textiles, there is no data available to support the proposed shift in consumer laundering behavior. Here, the results from a comprehensive literature review of nAg-textile life cycle studies are used to inform a cradle-to-grave life cycle impact assessment. Rather than assuming shifts in consumer behavior, the impact assessment is conducted in such a way that considers all laundering scenarios to elucidate the potential for reduced laundering to enable realization of a net life cycle benefit. In addition to identifying the most impactful stages of the life cycle across nine-midpoint categories, a payback period and uncertainty analysis quantifies the reduction in lifetime launderings required to recover the impacts associated with nanoenabling the textile. Reduction of nAg-textile life cycle impacts is not straightforward and depends on the impact category considered.